Dewatering, washing and classification screen devices are well known and comprise screen surfaces mounted in housings to which a liquid-solid slurry is fed for separation of the solids from the liquids on the screen surface. Previous devices include a highly polished concave curved screen surface or deck having an arcuate configuration formed to a configuration of 120.degree. arc segment of a circle. The screen surface is comprised of a plurality of equidistantly spaced, parallel, transverse separating bars having slot openings in the range of 50 to 150 microns formed therebetween. The slurry is fed in a substantially tangential direction to the concave side of the screen surface, at relatively high pressure, through spaced feed nozzles. Oversized material travels around the screen surface and is discharged from the device through an overflow outlet pipe. The liquid portion of the slurry, together with fines, passes through the slots in the screen surface and is discharged through an underflow outlet at the rear of the screen.
These screens have been highly successful in operation and are essentially free from maintenance costs as a result of the simple manner in which the devices function. In particular, the screens are used extensively for high capacity fine separation of fibrous non-abrasive solids in the pulp and paper industry where the screens are used for many process purposes, such as for example, as savealls or in fiber recovery. Additionally, the screens have found acceptance in the corn wet milling industry, where corn slurries must be separated from the fluid constituents. Although the screens are highly effective, they are subject to wear and must be frequently removed for reversal and replacement.
The design presently on the market utilizes a screen surface held in place inside the dewatering device by the feed nozzles, as well as by an arrangement of retainers and wedges. Once the screen is installed, additional gaskets and caulking must be applied to form a seal between the over and undersized compartments. This process involves the use of approximately twenty four bolts to properly secure the screen. Such an apparatus is shown in U.S. Pat. No. 4,202,777, Schall. All of these steps make the reversal or replacement of the screen surfaces time consuming and difficult. For example, the removal and reversal process takes two mechanics approximately eight hours. Further, since the work must be done inside the screen housing, the presence of noxious vapors and high temperatures aggravates the difficulties.
Numerous attempts have been made to provide a simple and cost effective screen assembly for a screen separation device, but none have fully overcome the difficulties discussed above. To illustrate, U.S. Pat. No. 4,113,626, Detcher, discloses a dewatering screen including a screen assembly that is held in position by a stationary pivot rod and a screw assembly. U.S. Pat. No. 3,835,999, Moore, discloses a dewatering apparatus utilizing a screen that pivots to a non-use position. Other devices include a disintegrating apparatus having an easily removable and replaceable screen assembly as disclosed in U.S. Pat. No. 1,185,620, Blum, as well as a filtering device utilizing spring biasing to properly position the filter as disclosed in U.S. Pat. No. 4,892,656, Pietzsch. Additionally, Gideon discloses a ledge for properly positioning a filter in U.S. Pat. No. 4,169,057.
The instant invention provides a screen assembly for use with solids-liquid separation devices which is simple, convenient, and easy to install and remove. As such, the instant invention overcomes the deficiencies associated with the prior devices and marks a substantial improvement in the usefulness of solids-liquid separation devices.